Telegraph system



.l. H. BELL.

TELEGRAPH SYSTEM. APPLICATION FILED NOV. 22. 1917.

Patented Oct. 26, 1920.

UNITED STATES PATENT OFFICE.

JOHN H. BELL, OF SOU'1'H ORANGE, NEW JERSEY,

ASSIGNOB TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEGRAPH SYSTEM.

Specification of Letters Patent.

Patented Oct. 26, 1920.

7 Application fled November 22, 1911. Serial no. 203,355.

New Jersey, have invented certain new and.

useful Improvements in Telegraph Systems,

of which the following is a full,clear, con't cise, and exact description. 1

nventlon relates to telegraph sysdnplex telegraphy. v

The principal object of this invention is to provide an improved system to revent interference with telegrap 10 receiving devices due to the efi'ects which usually arise through mutual induction between neighboring conductors and a telegraph line c1rcuit.

provide a system of secret service to prevent the possibility of a line circuit. belng tapped by unauthorized parties.

In telegraph working, it is well understood that when a telegraph line parallels other telegraph lines,-and also power circuits operated at so-called high potentials, inductive effects from the telegraph circuits and the power circuits may become accumulative in acting inductively on the telegraph circuit In certain situations such inductive disturbances are suflicient to mutilate or perhaps cause the telegraphic receiving devices to entirely fail in the proper translation of message signals.

In accordance with the present invention there is provided a so-called vibrating or self-aidin electroresponsive receiving device toget er with current impedance means and current draina e means whereby currents extraneous to t e message impulses are deflected from the impulse receiving devices.

In carrying out the so-called secret service feature of this invention the characteristics of the equipment described permit a source of alternating current to be connected in derived relation from a main telegraph line in such a manner that the alternating currents may divide and pass from the line circuit to ground at each terminal station. Therefore, in case the line were tapped by means of ordinary telegraphic equipment, the alternating currents being superimposed on the regular message currents which traverse the line circuits, they would cause such A further object of this invention is to receiving devices to respond and accordingly 1t woul not be possible to distinguish or read the telegraphic signals.

his invention is illustrated diagrammatlcally in the accompan ing drawing, in whlch, for the sake of c earness, only so much of a telegraphic equipment. has been shown as will be necessary standing of this invention. tems, and more particularly to systems of.

tions joined by a main line conductor L and since a clear understanding of the system may be had through a description of-operations by wh ch messages may be transmitted between the two stations, a message originating at the station A will first be traced. A telegraph transmitting key 1 normally connects a negatively poled and rounded-battery 2 with the apex of a ridge duplex formed by resistance units 4 and 5, a polar relay 10, an artificial line AL and the main line L. Current from the source 2 accordlngly divides, one portion traversing the resistance 5 and the artificial line AL to earth, While a like portion traverses the resistance unit 4, the line L, the windings 31 and 32 of a polar rela 30 at the station .B, an impedance unit 2 and an .artificial line AL to earth. A portion of the current arriving at the station B also traverses a resistance unit tive current 38, from which point a circuit may be traced through the winding 33 of the relay 30 and a resistance unit 35 to earth. A condenser charging circuit may also be traced from the armature 37 through the winding 34- of this relay and a condenser 36 to a clear unde'rto connect correspondingly to earth. A conductor 40 may be considered as extending from the armature 37 to a telegraph sounder or other suitable electroresponsive device on which telegraphic 1mpulses may be manifested.

At the station A, when the key 1 s depressed, the "negative battery 2 is dlsconnected and a positively poled line battery 3 connected to the dup exed line to traverse the circuits already traced for the first negative current. At the relay 30, the positive current causes the armature 37 to disconnect the battery 38 and to complete a circuit with a grounded source of positive current 39. At the instant the armature 37 severs the connection with the battery 38 and before it reaches the contact correspondin with the battery 39, the condenser 36 wi l discharge throu h the windings and 33 of this relay an the resistance unit 35 to earth. The direction of this discharge bein cumulative with the action of the positive cur-rent through the windings 31 and 32, operation of the relay 30 is, therefore, accelerated by the discharge force which aids in moving the armature 37 to connect with the battery 39. In the last mentioned position of the armature the condenser 36 will receive a charge of positive current, while steady current of like polarity will be connected through the winding 33 and the resistance 35 to earth. It may be pointed out that on the instant the armature 37 engages either one or the other of its contact stops, the action of steady current through the winding 33 will be neutralized by the effect of the condenser charging current through the winding 34, thereby leaving the armature 37 entirely under influence of the current which ma be present in the windings 31 and 32, t us insurin that a firm contact will be effected for a su ficient period to properly operate the receiving equipment assumed as connected to the conductor 40. After the condenser 36 has become fully charged, the steady current in the winding 34 acts in opposition to correspondingly poled signaling current in the windin s 31 and 32 to the extent that the force 0 the biasing effect on the armature 37 is relieved, thereby permitting it to respond more readily to the next inversely poled impulse of signaling current.

From the foregoing description, it will be clear that in response to changes in polarity set up in the line conductor L by means of the transmitting ke 1, the receiving relay 30 at the station will respond oled currents with the receiving lead 40. he frequency of the current changes set up by the key 1 is sufliciently low not to be seriously affected by the inductance of the im dance 27 and the windings 31 and 32 o the relay 30. Therefore, the telegraphic currents may to a predetermined extent divide throu h this relay circuit and the parallel circuit ormed thereon by the resistance 26.

In the case of extraneous or induced currents which may be set up in the line L by adjacent telegraph lines or power circuits as already mentioned, the relatively high frequency of the induced currents cause them to seek the path formed through the resistance 26 and the resistances 24 and 25, rather than the circuit formed through the windin of the relay and the im edance coil 27. T is invention also provi es that, in view of the extreme sensitiveness of the receiving relay 30, due to its self-aiding effects as already pointed out, the bridge arms of the duplex circuit, as the resistances 24 and 25 at the station B and the resistances 4 and 5 at station A, may each be of relatively low resistance and this is also true of the resistances 6 and 26. Therefore, in addition to traversing the resistance unit 6 or 26, disturbin currents also find a path through the bri ge resistance units 4 and 5 for the station A, and 24 and 25 for the lstation B to earth through the artificial Referring to the matter of the secret service features of this system, an alternating current generator 41 is shown legged or connected in branch relation from the main line conductor L to earth. Currents produced by this generator traverse the main line to the station B and, due to the arrangement of shunts thereat, are deflected from the receiving circuits of the polar relay 30 to traverse the resistance unit 26 and the bridge arm resistances 24 and 25 to earth through the artificial line AL. A portion of the currents from the generator 41 also traverse the main line to the station A, thence continuing over the corresponding circuits, as the resistance 6 and the brid arm resistances 4 and 5, through the arti cial line to earth at that point. The frequency of the currents from ;-the generator 41 should be sufliciently high to cause no appreciable effect on the operating circuits of receiving relays 10 or 30 at the terminal stations.

Since the equipment at the station A is typical of the equipment at the station B it will be obvious that operation of the transmitting key 21 at the latter station would alternately connect asource of negative current 22 and a source of positive current 23 with the duplex line and these current chan es onarriving at the station A continue t rough the windings 11 and 12 of a polar relay 10 to correspondingly controlan armature 17, whereby oppositely poled sources of current 18 and 19 may be applied to the conductor 20 to control a suitable telegraph receiving equipment (not shown). The windings 13 and 14 of the relay 20, together with a condenser 16 and a resistance unit 15, from the self-aiding circults for this relay, which operate inia'man-v ner similar to that already described for the-self-aiding circuits of the relay 30.

The arrangement shown in. Fig. .2 of-the drawin difiers from the arrangement. al-

ready escribed only in the omission of the resistance unit 6, to compensate for which it is contemplated that the bridge arm resistances 4 and 5 would be of a sufliciently. low value to properly drain inductive or non message currents from the of the relay 10.

In describing the alternate arrangement-{= 1 shown in Fig. 3, it willbe noted that the circult arrangement is a combination of the bridge duplex and the diiferential polar duplex, since the apex or outgoing con'nec tive point of the bridge arm resistances 4 and 5 is also connected to the neutral pointintermediate the windings ll and 12 of the polar relay 10.1 An impedance coil 28 interposed between the exterior terminal of the coil 11 and the line conductorL therefore:

establishes this winding in a series which parallels the bridgei-esistance 4, while the Impedance coil 7 connected in series with the 5 and the artificial line st'antially opaque tosuch. currents, but responsive, however, to message currents due to the relatively lowfrequency of the latter- In this arrangement the self-aiding circuits of the polar relay 20 are typical andwork in the same manner as the self-aiding cirfigures of the drawing a estates the arms of said bridge duplex.

'1917. cuits described in connection with the other i What is claimed is: I

1". A telegraph system comprising a mam line, an artificial line, polar duplex equipment for said lines, means for transmitting impulses over said lines at a substantially predetermined frequency, self-aiding relay means for the reception of said impulses, and means including an inductance and resistancefor rendering .said receiving means non-responsive to current of a frequency elatively higher than the frequency of said signal impulses. recelvmg. c rcu t .2; In 'a telegraph system,amain line, an

artificial line, bridge duplex equipment employing ratio arms for said lines, meansfor' the transmission of signaling impulses at a predetermined rate or frequenc over said lines, self-aiding relay means to orm a polar.

duplex. arrangement with respect to said lines for the reception of said mipulses, inductive means connected intermediate said relayfme'ans and said main and artificial lines respectivelyfor deflecting a portion of the current of said impulses from said impulse receivingmeanS to be drained through 3. In a telegraph system, a main line, a

equipments, means for transmitting impulses over said line at a relatively predetermined speed or frequency, a self-aiding polar relay for the reception of said impulses, means to render said impulse receiving means unresponsiveitocurrent changes on said line circuit'iof higherv speed or frequency than said signaling impulses and to cause said high frequency current changes to be deflected'throu'ghthe arms of sa d-bridge duplex' equipment.

myname I duplex equipment comprising a combination "of bridge and differential polar duplex J i In wltness whereof, I hereunto subscribe this 20th day of November, A. D.,

I JOHN H-L L; 

